The stream flows into the main river right before it reaches Harbin, a city of 10 million people in the northeastern province of Heilongjiang.

Zhang takes in the scene: Across the river, dust swirls around a construction site. Nearby, a rust-colored pipe empties into the stream. On the banks, a few small vegetable plots are nestled against the brown water.

To gather information, the amiable young man strikes up conversations with some of the locals.

Three laborers sit by the riverbank, a businessman perches on a ledge with a book, and several farmers work in the vegetable plots below.

Zhang begins firing off questions: What is being built? What flows from the pipe? Is the ground water safe for growing crops?

When he leaves, he has a series of notes, to verify later with other sources: The buildings across the river are to be new offices. A planned water treatment plant has been started, but construction has proceeded in fits and starts. The pipe emits wastewater from construction sites. And the farmers are able to grow vegetables – but must sell them far from town, as locals won’t eat food grown here.

None of the men comments on the smell. “They’ve been here so long, they think it’s normal,” Zhang says.

This is one of his regular “investigation trips.” For the past several years, Zhang, the head of an independent environmental group in Harbin called Green Longjiang, has organized groups of volunteers – mostly young people and university students – to be eyes and ears on the ground, monitoring how the government’s green policies are working in practice.

“I believe the government has the good intention,” he says. “But sometimes there is too little money, and sometimes the leader thinks he is right, just like a hero, but his decisions may be wrong. So we must keep checking.”

These investigative trips cover a range of topics – gathering information about pesticide use, disposal of household waste, and industrial pollution. The long­est trips are 15 days, usually organized during school holidays.

“When we go a factory, we talk to the leader,” he explains. “Then we talk to the people around to check whether what the leader says is right or not.”

In China, the enforcement of Beijing’s environmental priorities falls to lower levels of government. But a host of obstacles at the local level – including lack of staff, resources, and technical expertise, as well as corruption – often means a gap between official goals and the facts on the ground.

“In China, the central government pays more attention to the environment than before,” says Li Yanfang, an environmental law professor at Renmin University in Beijing. “But if a victim in the countryside has no good relationships with the outside, maybe no people pay attention.”

“Collecting reliable data is a major challenge,” says Yang Fuqiang, vice president of the Energy Foundation, a Beijing-based research center that advises international donors.

There are no national independent watchdogs to verify official statistics or claims, which can turn out to be wrong.

Mr. Yang cited, as an example, the difficulty of monitoring the output of thousands of small coal mines across China. In 2003, Beijing discovered that its prior estimates had failed to account for about 50 million tons of coal consumed annually (that’s roughly one-third the yearly output of coal giant West Virginia).

The result is that even as China’s government pays increasing attention to environmental protection, it’s sometimes difficult to assess results.

Zhang’s concern about the availability of environmental information was galvanized rather dramatically in 2005 when he was a student at the Harbin Institute of Technology.On Nov. 13 that year, a now-infamous chemical explosion at a factory upstream released 100 tons of benzene, which scientists classify as a dangerous carcinogen, into the Songhua River.

During the 10 days it took for the 50-mile-long chemical slick to drift downstream to Harbin, rumors spread of a pending disaster, but different levels of government offered contradictory information. None said what had happened.

In the absence of clear and complete information from either government or local media, there was panic. Residents weren’t sure whether to take shelter, stock up on food, or prepare first-aid kits. Some heard rumors of a coming earthquake.

Zhang went online to find information posted by eyewitnesses. He also received tips from a friend whose mother worked for the local water bureau – she was simply concerned about her son’s welfare.

He posted the information on message boards in the university cafeteria, along with notices urging students to stock up on bottled water.

A few days later, the Harbin government turned off water supplies to millions of people. Later, it confessed that the reason for the shutdown was a chemical spill.

Zhang says the city government took many swift and effective measures to contain the damage. But he seriously faults the government for not disclosing the reasons.

“After the chemical bomb, the pollution could not be stopped,” he says, “but the public still had the right to know what happened.”

Today his relationship with local environmental authorities is evolving, alongside expectations about environmental protection and public participation in China.

In a recent magazine article, deputy environmental minister Pan Yue wrote that the Chinese government needs to “call on citizens to participate in the environmental protection movement … otherwise, sustainable development will become a mere slogan.”

On some projects, the Harbin environmental bureau has given Zhang’s group its blessing.

This year, the group conducted a series of investigative trips to the nearby city of Shuang Cheng Shi to gather information about what kinds of pesticides farmers use. The government supported this initiative and even lent staff support.

Yet when he submitted a request last year to hold a memorial vigil on Nov. 23, the date the chemical spill reached Harbin – including distributing photos and pamphlets to keep the event in the public consciousness – the government tried to dissuade him.

Zhang held a small demonstration anyway. Interestingly, the government didn’t stop him.

This situation indicates the delicate dance between China’s emerging environmental groups and the government. Zhang says he feels that his collaborations with government help soften his frequent criticisms.

“Environmentalists who work collaboratively and constructively with government partners in a nonthreatening manner,” observes Drew Thompson, director of China Studies and Starr Senior Fellow at The Nixon Center in Washington, “are less likely to face opposition or restrictions from the government.”